A bit of quadratic trinomials help please?

Ok, so we're doing quadratic trinomials and I get the idea of it but sometimes I get a bit confused in equations (getting symbols mixed up, things around the wrong way) and I was wondering if somebody could give me a quick brush up on a few things about it or point me in the direction of someone who could? Thanks in advance.

Ok, so we're doing quadratic trinomials and I get the idea of it but sometimes I get a bit confused in equations (getting symbols mixed up, things around the wrong way) and I was wondering if somebody could give me a quick brush up on a few things about it or point me in the direction of someone who could? Thanks in advance.